Science 4XSD1 — specification explorer

1. Reproduction

• 4.1understand the differences between sexual and asexual reproductionUnit 2
• 4.2understand that fertilisation involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryoUnit 2
• 4.3describe the structures of an insect-pollinated and a wind-pollinated flower, and explain how each is adapted for pollinationUnit 2
• 4.4understand that the growth of the pollen tube followed by fertilisation leads to seed and fruit formationUnit 2
• 4.5practical: investigate the conditions needed for seed germinationUnit 2
• 4.6understand how germinating seeds utilise food reserves until the seedling can carry out photosynthesisUnit 2
• 4.7understand that plants can reproduce asexually by natural methods (illustrated by runners) and by artificial methods (illustrated by cuttings)Unit 2
• 4.8understand how the structure of the male and female reproductive systems are adapted for their functionsUnit 2
• 4.9understand the roles of oestrogen and progesterone in the menstrual cycleUnit 2
• 4.11describe the role of the placenta in the nutrition of the developing embryoUnit 2
• 4.12understand how the developing embryo is protected by amniotic fluidUnit 2
• 4.13understand the roles of oestrogen and testosterone in the development of secondary sexual characteristicsUnit 2

2. Inheritance

• 4.14understand that the genome is the entire DNA of an organism and that a gene is a section of a molecule of DNA that codes for a specific proteinUnit 2
• 4.15understand that the nucleus of a cell contains chromosomes on which genes are locatedUnit 2
• 4.19understand how genes exist in alternative forms called alleles, which give rise to differences in inherited characteristicsUnit 2
• 4.20understand the meaning of the terms: dominant, recessive, homozygous, heterozygous, phenotype, and genotypeUnit 2
• 4.22understand that most phenotypic features are the result of polygenic inheritance rather than single genesUnit 2
• 4.23describe patterns of monohybrid inheritance using a genetic diagramUnit 2
• 4.24understand how to interpret family pedigreesUnit 2
• 4.25predict probabilities of outcomes from monohybrid crossesUnit 2
• 4.26understand how the sex of a person is controlled by one pair of chromosomes, XX in a female and XY in a maleUnit 2
• 4.27describe the determination of the sex of offspring at fertilisation, using a genetic diagramUnit 2
• 4.28understand how division of a diploid cell by mitosis produces two cells that contain identical sets of chromosomesUnit 2
• 4.29understand that mitosis occurs during growth, repair, cloning and asexual reproductionUnit 2
• 4.30understand how division of a cell by meiosis produces four cells, each with half the number of chromosomes, and that this results in the formation of genetically different haploid gametesUnit 2
• 4.31understand how random fertilisation produces genetic variation of offspringUnit 2
• 4.32know that in human cells the diploid number of chromosomes is 46 and the haploid number is 23Unit 2
• 4.33understand that variation within a species can be genetic, environmental, or a combination of bothUnit 2
• 4.34understand that mutation is a rare, random change in genetic material that can be inheritedUnit 2
• 4.38explain Darwin’s theory of evolution by natural selectionUnit 2
• 4.39understand how resistance to antibiotics can increase in bacterial populations, and appreciate how such an increase can lead to infections being difficult to controlUnit 2

1. The organism in the environment

• 5.1understand the terms: population, community, habitat and ecosystemUnit 2
• 5.2practical: investigate the population size of an organism in two different areas using quadratsUnit 2
• 5.5understand how abiotic and biotic factors affect the population size and distribution of organismsUnit 2

2. Feeding relationships

• 5.6understand the names given to different trophic levels, including producers, primary, secondary and tertiary consumers, and decomposersUnit 2
• 5.7understand the concepts of food chains, food webs, pyramids of number, pyramids of biomass and pyramids of energy transferUnit 2
• 5.8understand the transfer of substances and energy along a food chainUnit 2
• 5.9understand why only about 10 per cent of energy is transferred from one trophic level to the nextUnit 2

3. Cycles within ecosystems

• 5.10describe the stages in the carbon cycle, including respiration, photosynthesis, decomposition and combustionUnit 2

4. Human influences on the environment

• 5.12understand the biological consequences of pollution of air by sulfur dioxide and carbon monoxideUnit 2
• 5.13understand that water vapour, carbon dioxide, nitrous oxide, methane and Chlorofluorocarbons (CFCs) are greenhouse gasesUnit 2
• 5.14understand how human activities contribute to greenhouse gasesUnit 2
• 5.15understand how an increase in greenhouse gases results in an enhanced greenhouse effect and that this may lead to global warming and its consequencesUnit 2
• 5.16understand the biological consequences of pollution of water by sewageUnit 2
• 5.17understand the biological consequences of eutrophication caused by leached minerals from fertiliserUnit 2

1. Food production

• 6.1describe how glasshouses and polythene tunnels can be used to increase the yield of certain cropsUnit 2
• 6.2understand the effects on crop yield of increased carbon dioxide and increased temperature in glasshousesUnit 2
• 6.3understand how the use of fertiliser can increase crop yieldUnit 2
• 6.4understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with crop plantsUnit 2
• 6.5understand the role of yeast in the production of food, including breadUnit 2
• 6.6practical: investigate the role of anaerobic respiration by yeast in different conditionsUnit 2
• 6.7understand the role of bacteria (Lactobacillus) in the production of yoghurtUnit 2
• 6.8understand the use of an industrial fermenter and explain the need to provide suitable conditions in the fermenter, including aseptic precautions, nutrients, optimum temperature and pH, oxygenation and agitation, for the growth of micro- organismsUnit 2

2. Selective breeding

• 6.10understand how selective breeding can develop plants with desired characteristicsUnit 2
• 6.11understand how selective breeding can develop animals with desired characteristicsUnit 2

3. Genetic modification (genetic engineering)

• 6.12understand how restriction enzymes are used to cut DNA at specific sites and ligase enzymes are used to join pieces of DNA togetherUnit 2
• 6.13understand how plasmids and viruses can act as vectors, which take up pieces of DNA, and then insert this recombinant DNA into other cellsUnit 2
• 6.14understand how large amounts of human insulin can be manufactured from genetically modified bacteria that are grown in a fermenterUnit 2
• 6.15understand how genetically modified plants can be used to improve food productionUnit 2
• 6.16understand that the term ‘transgenic’ means the transfer of genetic material from one species to a different speciesUnit 2